U.S. patent number 4,541,019 [Application Number 06/444,712] was granted by the patent office on 1985-09-10 for recording system for recording data on tape in a disk-recording format.
This patent grant is currently assigned to Cipher Data Products, Inc.. Invention is credited to Normand E. Precourt.
United States Patent |
4,541,019 |
Precourt |
September 10, 1985 |
Recording system for recording data on tape in a disk-recording
format
Abstract
A tape recording system for connection to a controller of a
floppy disk data recording system for recording data in a stream on
a recording tape in the same format that data is recorded on a disk
by the disk data recording system. A control processor responds to
sensing a beginning-of-stream indicator on the tape (a) by causing
an initial gap to be erased in the tape stream adjacent the
beginning-of-stream indicator and (b) by next providing an initial
beginning-of-segment index pulse to the controller. The control
processor responds to the combination of (a) a gate signal from the
controller provided simultaneously with a formatting signal and (b)
the sensing that the length of tape transported past the transducer
head following provision of a beginning-of-segment index pulse
corresponds to the length of a concentric track on a disk (a) by
providing an end-of-segment index pulse to the controller, (b) by
next causing an inter-segment gap to be erased in the tape stream
and (c) by finally providing another beginning-of-segment index
pulse to the controller. The controller responds to the
beginning-of-segment index pulse from the control processor by
providing to the transducer head a formatting signal for recording
a segment that ends when the following end-of-segment index pulse
is provided to the controller by the control processor; and the
transducer head records the segment in the tape stream between
consecutive erased gaps.
Inventors: |
Precourt; Normand E. (San
Diego, CA) |
Assignee: |
Cipher Data Products, Inc. (San
Diego, CA)
|
Family
ID: |
23766031 |
Appl.
No.: |
06/444,712 |
Filed: |
November 26, 1982 |
Current U.S.
Class: |
360/15;
G9B/20.033; G9B/15; G9B/5.308; 360/48 |
Current CPC
Class: |
G06F
3/0601 (20130101); G11B 15/00 (20130101); G11B
5/86 (20130101); G11B 20/1262 (20130101); G06F
3/0682 (20130101); G11B 2220/90 (20130101) |
Current International
Class: |
G11B
15/00 (20060101); G11B 20/12 (20060101); G11B
5/86 (20060101); G06F 3/06 (20060101); G11B
005/86 () |
Field of
Search: |
;360/15,48,50,72.1,72.2,72.3,71,2MSFile |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Navy TDB vol. 4, No. 8, "Cartridge Tape Formatter and Interface",
Boland, Aug. 1979..
|
Primary Examiner: McElheny, Jr.; Donald
Assistant Examiner: Garland; Steven R.
Attorney, Agent or Firm: Baker, Maxham, Callan &
Jester
Claims
I claim:
1. A recording tape data recording system for connection to a host
controller of a floppy disk data recording system for recording
data in a stream on a recording tape in the same format that data
is recorded on a floppy disk by the floppy disk data recording
system, wherein the host controller is operable in a formatting
mode in which the host controller responds to a first-received
index pulse by providing a formatting write data signal to record a
segment that has a format including a first fill field, followed by
a predetermined number of sectors that individually include an
address field and a data field, followed by a second fill field
until a second index pulse is received, wherein the host controller
is operable in a write mode in which the host controller responds
to recognition of a predetermined address read from an accessed
recorded sector by providing a recording write data signal to write
data in the data field of the accessed sector, and wherein the host
controller provides a write gate signal simultaneously with the
provision of either write data signal; said recording tape data
recording system comprising
a read/write transducer head for connection to the host controller
for reading data from the tape stream, or writing data in the tape
stream, or erasing in the tape stream;
transport means for transporting the tape past the transducer head
to cause the transducer head to access a stream on the recording
tape;
first sensing means for sensing a beginning-of-stream indicator on
the recording tape;
second sensing means coupled to the transport means for sensing the
length of tape transported past the transducer head; and
a control processor for connection to the host controller and
coupled to the transducer head and the first and second sensing
means for responding to the first sensing means sensing the
beginning-of-stream indicator (a) by providing an erase command to
the transducer head for causing an initial gap to be erased in the
tape stream adjacent the beginning-of-stream indicator and (b) by
next providing an initial beginning-of-segment index pulse to the
host controller, and for responding to the combination of (a) the
write gate signal from the host controller that is provided
simultaneously with the formatting write data signal and (b) the
second sensing means sensing that the length of tape transported
past the transducer head following provision of a
beginning-of-segment index pulse corresponding to the length of a
concentric track on a said floppy recording disk (a) by providing
an end-of-segment index pulse to the host controller, (b) by next
providing an erase command to the transducer head for causing an
inter-segment gap to be erased in the tape stream and (c) by
finally providing another beginning-of-segment index pulse to the
host controller;
whereby, when operated in the formatting mode, the host controller
responds to each beginning-of-segment index pulse from the control
processor by providing to the transducer head a formatting write
data signal for recording a segment that ends when the following
end-of-segment index pulse is provided to the host controller by
the control processor; and
wherein the transducer head responds to the formatting write data
signal provided by the host controller by recording the segment in
the tape stream between consecutive erased gaps.
2. A system according to claim 1, wherein the host controller
further provides step command signals for indicating that a
different segment should be accessed other than the presently
accessed segment; and
wherein the control processor further includes
a first counter for responding to said step command signals by
providing a first count indicating the segment that should be
accessed;
a second counter for responding to detection of erased gaps in the
tape stream by providing a second count indicating the segment
being accessed; and
means for comparing said first and second counts and for providing
an access command signal to the transport means in response to said
comparison to cause the transducer head to access the segment that
should be accessed.
Description
BACKGROUND OF THE INVENTION
The present invention generally pertains to data recording systems
and is particularly directed to a system for recording data on tape
in a disk recording format.
The five and one-quarter inch Winchester recording disk which
provides substantial storage capacity and rapid data access is
becoming increasingly popular as a principal memory for personal
and small business computers, which until recently, used
exclusively flexible or floppy disk memories. A five and
one-quarter inch Winchester disk may have a memory storage capacity
of, for example, fifty-five megabytes. On the other hand, a typical
floppy disk may have a storage capacity of only one-quarter
megabyte.
Many computer systems have backup memory devices to assure against
malfunctions or physical damage that could destroy the principal
data bank. In the past, in personal and small business computer
systems, the backup storage unit has typically consisted of a
second floppy disk drive. However, the increasing use of five and
one-quarter inch Winchester disk drives in personal and small
business computers has created a need for greater backup storage.
Floppy disk drives are unsuitable for use as backup storage for a
five and one-quarter inch Winchester disk drive because the hard
disk stores many times more information than a single floppy disk.
For example, forty one-quartermegabyte floppy disks would be needed
to back up one ten megabyte Winchester disk drive, making backup
storage a time-consuming inconvenience for the operator.
Magnetic tape is a more practical form of backup storage for the
five and one-quarter inch Winchester recording disk.
A typical prior art system for recording data on a floppy recording
disk 9 is shown in FIG. 1. This prior art system includes a disk
recorder controller 10, a host interface circuit 11, a control
logic circuit 12, a write logic circuit 13, a read logic circuit
14, a spindle 15, a transducer head assembly 16, a stepper motor
17, a drive motor 18, a motor drive circuit 19, a "track 00" switch
20, a write protect switch 22, an index pulse LED (light emitting
diode) 23 and an index pulse detector 24. The disk 9 is contained
in a diskette 21, and is engaged on the spindle 15 for rotation
within the diskette 21.
A CPU (central processing unit) 25 is connected to the disk
recorder controller 10 by a bus 26. Data, addresses and control
signals are communicated between the CPU 25 and the disk recorder
controller 10 over the bus 26.
Signals are communicated between the disk recorder controller 10
and the control logic circuit 12 via a bus 27, the host interface
circuit 11 and lines 29, 30, 31, 32 and 33.
Step command signals and a direction select signal from the disk
recorder 10 are provided on lines 29 and 30 respectively to the
control logic circuit 12 for controlling which track of the
recording disk 9 is accessed by the transducer head. The recording
disk 9 has concentric tracks. The control logic circuit 12 provides
stepper A, B, C and D control signals on lines 35, 36, 37 and 38 to
the stepper motor 17. The control logic circuit 12 provides a
"track 00" signal on line 31 to the disk recorder controller 10
when the transducer head is accessed to the outermost track on the
disk. The control logic circuit derives the "track 00" signal from
line 40 which is connected to the "track 00" switch 20, together
with a common line 41.
A "motor on" signal from the disk recorder controller 10 is
provided on line 33 to the control logic circuit 12 for controlling
the drive motor 18. The drive motor 18 is coupled to the spindle 15
for rotating the turntable so that the transducer head can access
various locations on each concentric track of the recording disk.
The control logic circuit 12 provides motor drive signals on line
42 to the motor driver circuit 19, which in turn provides motor
control signals on line 43 to the drive motor 18. A speed signal is
provided on line 45 to the motor driver circuit 19 from a
tachometer attached to the drive motor 18 for completing a servo
loop for controlling the speed of the drive motor 18.
The control logic circuit 12 provides a "head load solenoid" signal
on line 46 to the transducer head assembly 16 for placing said
transducer head in contact with the recording disk 9, thereby
allowing recording on the recording disk 9.
The control logic circuit 12 provides an index pulse on line 32 to
the disk recorder controller 10 for every rotation of the disk 9.
The control logic circuit 12 generates the index pulse on line 32
in response to receiving an index pulse detection signal on line 47
from the index pulse detector 24. The index pulse detector 24
detects light from the index pulse LED 23 that is transmitted
through a hole 48 in the disk 9 at a fixed point during each
rotation of the disk 9. The index pulse LED 23 is energized by a
signal on line 49 from the control logic circuit 12.
The format for recording on the recording disk 9 is keyed to the
reception of index pulses by the disk recorder controller 10. The
controller 10 responds to the index pulse when in a formatting mode
by providing a recording signal to the write logic circuit 13 on
line 51 for formatting a recorded track on the disk 9. The
recording signal for each track includes a first fill field,
followed by a predetermined number of sectors including identifying
addresses and data, followed by a second fill field until the index
pulse is again received upon completion of one revolution of the
disk 9. Recording is enabled only when a "write gate" signal is
provided by the disk recorder controller 10 to the write logic
circuit on line 52. The write logic circuit 13 provides the signal
to be recorded to the transducer head via line 53.
A write protect switch 22 is provided for connection to a recording
disk when it is desired to prevent recording on the disk 9. The
write protect switch 22 is connected to the write logic circuit 13
by a signal line 54 and a common line 55. The write logic circuit
13 provides a "write protect" signal on line 57 to the disk
recorder controller 10 to prevent the controller 10 from providing
recording signals on write data line 51.
The signals on lines 51, 52 and 57 are communicated between the
disk recorder controller 10 and the write logic circuit via bus 27
and the host interface circuit 11.
The read logic circuit 14 receives signals read by the transducer
head on line 59 and conditions and provides the received read data
signals on line 61 to the disk recorder controller 10 via the host
interface circuit 11 and bus 27.
SUMMARY OF THE INVENTION
The present invention is a recording tape data recording system for
connection to a host controller of a floppy disk data recording
system for recording data in a stream on a recording tape in the
same format that data is recorded on a floppy disk by the floppy
disk data recording system. That such system is a more practical
form of backup storage for a hard recording disk has been pointed
out above. A stream is one of a number of longitudinal areas on a
tape defined by the accessed position of a recording head.
One feature of the system of the present invention is that the disk
recorder controller of the prior art disk recording system
described hereinabove can be connected to the system of the present
invention as the host controller thereby economically reducing
development and production costs.
The host controller is operable in a formatting mode in which the
host controller responds to a first-received index pulse by
providing a formatting write data signal to record a segment that
has a format including a first fill field, followed by a
predetermined number of sectors that individually include an
address field and a data field, followed by a second fill field
until a second index pulse is received. The host controller also is
operable in a write mode in which the host controller responds to
recognition of a predetermined address read from an accessed
recorded sector by providing a recording write data signal to write
data in the data field of the accessed sector. The host controller
provides a write gate signal simultaneously with the provision of
either write data signal.
The recording system of the present invention includes a read/write
transducer head for connection to the host controller for reading
data from the tape stream, or writing data in the tape stream, or
erasing in the tape stream; transport apparatus for transporting
the tape past the transducer head to cause the transducer head to
access a stream on the recording tape; a first sensor for sensing a
beginning-of-stream indicator on the recording tape; a second
sensor coupled to the transport apparatus for sensing the length of
tape transported past the transducer head; and a control
processor.
The control processor is adapted for connection to the host
controller and is coupled to the transducer head and the first and
second sensors for responding to the first sensor sensing the
beginning-of-stream indicator (a) by providing an erase command to
the transducer head for causing an initial gap to be erased in the
tape stream adjacent the beginning-of-stream indicator and (b) by
next providing an initial beginning-of-segment index pulse to the
host controller, and for responding to the combination of (a) the
write gate signal from the host controller that is provided
simultaneously with the formatting write data signal and (b) the
second sensor sensing that the length of tape transported past the
transducer head following provision of a beginning-of-segment index
pulse corresponds to the length of a concentric track on a floppy
recording disk (a) by providing an end-of-segment index pulse to
the host controller, (b) by next providing an erase command to the
transducer head for causing an inter-segment gap to be erased in
the tape stream and (c) by finally providing another
beginning-of-segment index pulse to the host controller.
When operated in the formatting mode, the host controller responds
to each beginning-of-segment index pulse from the control processor
by providing to the transducer head a formatting write data signal
for recording a segment that ends when the following end-of-segment
index pulse is provided to the host controller by the control
processor; and the transducer head responds to the formatting write
data signal provided by the host controller by recording the
segment in the tape stream between consecutive erased gaps.
Additional features of the present invention are described in
relation to the description of the preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram of a prior art system for recording data
on a recording disk.
FIG. 2 is a block diagram of a system according to the present
invention for recording data in a stream on a tape in a disk
recording format.
FIG. 3 is a functional block diagram for the microprocessor of the
system of FIG. 2.
FIG. 4 is a process flow diagram for the process logic circuit
shown in FIG. 3.
FIG. 5 illustrates the format in which the system of the present
invention records in a stream on a recording tape.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the system of the present invention is
designed for use in the preferred embodiment of the cartridge tape
drive described in a United States patent application by William M.
Barton, Jr., John F. Murphy, Karl B. Offerman and Richard G. Fisher
entitled "Cartridge Tape Drive", filed Nov. 15, 1982, Ser. No.
441,762, assigned to the same assignee as the present application,
the disclosure of which prior application is incorporated herein by
reference.
The tape cartridge drive described therein is designed for
receiving a magnetic tape cartridge 20 (FIG. 2) similar to that
described in ANSI standard X3.55-1977. One such cartridge is model
DC300XL sold by Minnesota Mining and Manufacturing Company, Saint
Paul, Minn., U.S.A. The cartridge 20 contains one-quarter inch
width magnetic recording tape 44.
The preferred embodiment of the recording system of the present
invention is shown in FIG. 2 in engagement with a tape cartridge
20. The system includes a capstan drive roller 56, a transducer
head 62, a host controller 65, a beginning-of-stream sensing
mechanism 70, a write protect sensor 76, a stepper motor 78, a
transport drive motor 80, a "cartridge in place" sensor 82, a
microprocessor 84, a host interface circuit 86, a read/write logic
circuit 88 and a "servo and control logic" circuit 90.
The cartridge 20 has a cut-out region 58 along one side edge
thereof which is conformably shaped for receiving the transducer
head 62 so that the head 62 can make contact with the tape 44 as
illustrated in FIG. 2. The cartridge 20 also has a cut-out region
64, where the capstan drive roller 56 contacts a belt capstan
roller 50 within the cartridge 20. The belt capstan roller 50 has
an upper larger portion and a lower smaller portion. The larger
portion of the drive belt capstan 50 extends above and beyond the
magnetic tape 44 so that the capstan drive roller 56 can engage the
belt capstan roller without touching the tape 44.
The cartridge 20 also has a mirror positioned behind a window which
is utilized in connection with the beginning-of-stream sensing
mechanism 70 for sensing the load point and early warning
indications on the tape 44. The cartridge 20 also has a write
protect mechanism consisting of a rotatable half cylinder
positioned in front of a cut-out region. The write protect sensor
76 determines whether or not such cut-out region is blocked by the
semi-circular portion of the file protect cylinder and provides a
write protect signal on line 69 when the cut-out region is not
blocked.
The transducer head 62 is vertically positionable by energizing the
stepper motor 78 to select any one of a plurality of different
streams on the tape 44. The capstan drive roller 56 is mounted on
the upper end of the shaft of the transport drive motor 80. The
sensor 82 is mounted adjacent to the write protect sensor 76 and is
utilized to detect when a cartridge 20 is in place within the
drive.
The host controller 65 is identical to the disk recorder controller
10 in the prior art disk recording system described above in
relation to FIG. 1. The host controller 65 communicates with the
CPU 25 over the bus 26. The host controller 65 provides a write
data signal on line 71, a write gate signal on line 73, step
command signals on line 75, a direction select signal on line 77
and a "motor on" signal on line 79 in the same manner as the
like-identified signals are provided by the disk recorder
controller 10 on lines 51, 52, 29, 30 and 33 respectively in the
prior art disk recorder system of FIG. 1. The host controller 65
processes a read data signal received on line 81, a write protect
signal received on line 83, a "track 00" signal received on line
85, and index pulses received on line 87 in the same manner as the
like-identified signals received by the disk recorder control 10
from lines 61, 57, 31 and 32 respectively are processed in the
prior art disk recorder system of FIG. 1.
The write data signal on line 71 from the host controller 65 is
provided to the transducer head 62 via the host interface circuit
86, line 89, the read/write logic circuit 88 and line 91. The read
data signal on line 81 is provided to the host controller 65 from
the transducer head 62 via the line 91, the read/write logic
circuit 88, line 93 and the host interface circuit 86.
The write gate signal on line 73, the step command signals on line
75, the direction select signal on line 77 and the "motor on"
signal on line 79 from the host controller 65 are provided to the
microprocessor 84 via the host interface circuit 86 and a bus 94.
The write protect signal on line 83, the "track 00" signal on line
85 and the index pulses on line 87 are provided to the host
controller 65 from the microprocessor 84 via the bus 94 and the
host interface circuit 86.
The microprocessor 84 is enabled by a "cartridge in place" signal
provided on line 95 from the sensor 82 when the cartridge 20 is in
place in the cartridge tape drive.
The microprocessor 84 includes logic circuits and firmware.
Referring to FIG. 3, the microprocessor functions as though it
effectively includes a process control logic circuit 97, an access
control logic 98, an index pulse generator 99, an actual segment
counter 100 and an addressed segment counter 101.
A process flow diagram for the process control logic circuit 97 is
shown in FIG. 4.
Referring to FIG. 3, the process control logic circuit 97 responds
to step commands on line 75 and the direction select signal on line
77 by providing count pulses on line 103 to the addressed segment
counter 101. The addressed segment counter 101 provides an
addressed count signal on line 104 indicating the segment in the
stream on the tape 44 that should be accessed by the transducer
head 62.
The actual segment counter 100 provides an actual count signal on
line 105 indicating the segment being accessed by the transducer
head 62.
The process control logic circuit 97 compares the addressed count
signal on line 104 with the actual count signal on line 105 and
responds to such comparison by providing an access command signal
on line 106 to the access control logic circuit 98 for controlling
the transport apparatus in the cartridge tape drive to cause the
transducer head 62 to access the segment that should be accessed.
The operation of the actual segment counter in providing the actual
count signal on line 105 is described below in relation to the
description of the process flow diagram of FIG. 4.
Referring to both FIGS. 2 and 3, the access control logic circuit
98 responds to the "motor on" signal on line 79 and the access
command signal on line 106 by providing an access drive signal on
line 107 to the "servo and control logic" circuit 90. The servo and
control logic circuit 90 provides forward and reverse signals on
lines 108 and 109 respectively to the transport drive motor 80. A
tachometer (not shown) coupled to the capstan drive roller 56
provides a speed/distance indication signal on line 110 to the
servo and control logic circuit 90 to complete a servo loop for
controlling the speed at which the tape 44 is transported past the
transducer head 62.
The servo and control logic circuit 90 further responds to the
access drive signal on line 107 by providing a head position signal
on line 111 to the stepper motor 78 for controlling the stepper
motor 78 to cause the transducer head to access the stream on the
tape 44 that contains the segment that should be accessed.
When the transport drive motor 80 is driven in the forward
direction for recording, the load point indication provided on the
tape 44 as manufactured is sensed by the sensing mechanism 70 as
the fully rewound tape 44 begins to be transported past the
transducer head 62. When the transport drive motor is driven in the
reverse direction for recording, the early warning indication
provided on the tape 44 as manufactured is sensed by the sensing
mechanism 70 as the fully wound tape 44 begins to be transported
past the transducer head 62. The sensing mechanism provides a
beginning-of-stream indication signal on line 112 in response to
sensing the load point indication on the tape 44 when recording in
the forward direction and in response to sensing the early warning
indication on the tape 44 when recording in the reverse direction.
The load point and 30 early warning indications thereby serve as
beginning-of-stream indicators, and typically are provided on the
tape 44 in the form of a hole 113, as in FIG. 5, which illustrates
a formatted stream on the tape 44. FIG. 5 is not drawn to
scale.
The process control logic circuit 97 responds to the
beginning-of-stream signal on line 112 by providing an erase
command signal on line 114 to the read/write logic circuit 88 to
cause an erase signal to be provided on line 115 to the transducer
head 62 for erasing an initial gap 116 of a predetermined length in
the stream on the tape 44. At the conclusion of the initial gap,
the process control logic circuit 97 provides an index command on
line 118 to the index pulse generator 99. The index pulse generator
99 responds to the index command on line 118 by providing an
initial beginning-of-segment index pulse on line 87 to the host
controller 65.
The host controller 65 responds to a beginning-of-segment index
pulse on line 87 when in a formatting mode by providing a recording
segment signal to the transducer head 62 via line 71 for formatting
a recorded stream on the tape 44. Referring to FIG. 5, each
recorded segment 120 includes a first fill field 121, followed by a
predetermined number of sectors 1, 2, . . . n including identifying
addresses and data, followed by a second fill field 122 until an
end-of-segment index pulse is provided on line 87 by the
microprocessor 84 to the host controller 65. The segment length is
equivalent to the length of a concentric track on the recording
disk 9 (FIG. 1).
The host controller 65 also provides the write gate signal on line
73 whenever a recording segment signal is provided on line 71 to
the transducer head 62 for formatting a recorded stream on the tape
44. The write gate signal on line 73 causes the process control
logic circuit to provide a write command signal on write/erase line
114 to the read/write logic circuit 88 to enable the recording
segment signal on line 71 to be provided to the transducer head 62
via line 91.
The speed/distance indication signal on line 110 is passed by the
"servo and control logic" circuit 90 via line 119 as a distance
signal to the process and control logic circuit 97. The process and
control logic circuit 97 processes the distance signal on line 119
to determine the length of tape 44 from the beginning of each
segment 120. The process control logic circuit 97 responds to such
determination by providing index commands on line 118 to the index
pulse generator 99 to cause the index pulse generator 99 to
generate end-of-segment index pulses on line 87 as a function of
the length of tape transported past the transducer head 62
following each beginning-of-segment index pulse. The end-of-segment
index pulses on line 87 are provided at predetermined fixed-length
intervals along the stream on the tape 44 to define segments of
uniform length.
The process control logic circuit 97 provides an erase command on
line 114 to the read/write logic circuit 88 for erasing an
inter-segment gap 124 of a predetermined length in the stream
following provision of each end-of-segment index pulse when a write
gate signal is simultaneously received on line 73, thereby
indicating that the host controller 65 is in a formatting mode.
At the conclusion of each of the erase commands defining
inter-segment gaps 124, the process control logic circuit 97
provides an index command to the index pulse generator 99, which in
turn provides a beginning-of-segment index pulse following each
inter-segment gap 124 in the formatted stream. The host controller
65 responds to each beginning-of-segment index pulse on line 87
when in a formatting mode by providing a segment recording signal
on line 71 as described above.
The microprocessor 84 provides the write protect signal from line
69 to the host controller 65 via line 83.
The operation of the process control logic circuit 97 is further
described with reference to the process flow diagram of FIG. 4.
At the start, the process control logic circuit 97 looks for a
beginning-of-stream signal on line 112. If a beginning-of-stream
signal is received on line 112, a command signal is provided on
line 114 to cause the initial gap 116 to be erased in the stream by
the transducer head 62. If a beginning-of-stream signal is not
received on line 112 the process control logic circuit merely
searches for a segment detection signal on line 117 which is
provided upon the trailing edge of an inter-segment gap 124 being
recognized by the read/write logic circuit 88 from the signal read
by the transducer head 62.
Upon either the conclusion of the erase command signal on line 114
for generating the initial gap 113, or the receipt of a segment
detection signal on line 117, the process control logic circuit 97
provides an index command signal on line 118 for causing a
beginning-of-segment index pulse to be generated and provided on
line 87 by the index pulse generator 99.
Upon providing the index command signal on line 118, the process
control logic control circuit 97 also provides a read enable signal
on line 126 to the read/write logic circuit 88 for enabling data
read by the transducer head to be provided over line 93 and thence
over line 81 to the host controller 65.
The process control logic circuit 97 then determines by processing
the distance signal received on line 119 whether a predetermined
length of tape 44 defining a recorded segment 120 has been
transported past the recording head 62, and upon each such
segment-length of tape having been so transported, further
determines whether a write gate signal is being received on line
73.
In either case, the read enable signal on line 126 is discontinued
so as to disable the provision of the read data signal on line 93
to the host controller via the host interface circuit 86 and line
81.
If the write gate signal is being received on line 73, an index
command is provided on line 118 to cause the index pulse generator
99 to generate and provide an end-of-segment index pulse on line
87; and an erase command is provided on line 114 to cause an
inter-segment gap 124 to be erased in the stream.
If the write gate signal is not being received on line 73, passage
of a segment-length of tape past the transducer head 62 is
determined. The process control logic circuit 97 searches for a
segment detection signal on line 117 which indicates that the
trailing edge of an inter-segment gap 124 has been recognized.
At this point in the process, either the conclusion of the erase
command signal on line 114 or the receipt of a segment detection
signal on line 117 results in the process logic control circuit 97
providing an update count signal on line 132 to increment the count
in the actual segment counter 100 by one. The actual segment
counter 100 is reset at the beginning of each stream by a reset
signal provided on line 130 by the process control logic circuit 97
in response to receipt of the beginning-of-segment signal on line
112.
The process control logic circuit 97 provides a "track 00" signal
on line 85 when the actual count signal provided on line 105
indicates that the first segment in the stream is being accessed by
the transducer head 62.
After the count is updated, the process control logic circuit
determines whether the transducer head 62 is entering the correct
segment of the formatted stream as the tape is being transported in
the direction in which data is recorded in the accessed stream. If
so, an index command is provided on line 118 to cause the index
pulse generator 99 to generate and provide another
beginning-of-segment index pulse on line 87 and the process
continues with the read enable signal being provided on line 126,
etc.
If it is determined that the transducer head 62 is not entering the
correct segment, the process control logic circuit 97 provides an
access command on line 106 to control the transport drive motor 80
to cause the transducer head to access either the beginning of the
stream or the middle of the segment prior to the segment that
should be accessed. A count update signal is then provided on line
132 to the actual segment counter 100 and the process is repeated
from the start as indicated by the process flow diagram of FIG.
4.
When the host controller 65 is in a read/write mode, it responds to
an address requirement from the CPU 27 by searching the formatted
stream accessed by the transducer head 62 for the recorded address
indicated by the address signal; and the process control logic
circuit 97 responds to the comparison of the count signals on lines
104 and 105 by providing an access command signal on line 106 that
causes the transducer head 62 to access the segment containing the
sector indicated by the address signal.
* * * * *